Holesaw center finder and guide - simply saw a larger hole in a small one

I needed a tool to help me drill a 68mm hole in my bathroom ceiling, where a ~60mm hole already was. Without a guide for the centerdrill of the holesaw, it would just wiggle around and scratch the surface. (I’ve done a lot of such holes before)

This tool does exactly the job. You have to print a top and a bottom part. For the top part You can choose between M4 heat inserts or M4 hex nuts to press in. 
For the bottom part, choose between 60, 65, 70 or 75 (diameter of the existing hole). 
It will also work if Your existing hole is slightly smaller or larger than the described diameter, but it will not exactly be in the center. 

Printing instructions: PLA worked fine for me, I printed the parts with 0,2mm layers, 4 perimeters and 20% gyroid infill to make them really strong. Print the parts orientated as You have downloaded them. 

Besides the two printed parts, You need two M4 Screws 30mm and two M4 heat insert nuts OR two M4 hex nuts.

The guidehole is made for centerdrills up to 7mm. You can try to drill it bigger if you have a larger centerdrill, or leave me a comment. 

For usage: press in the M4 nuts (heat insert or hex) and screw the two parts together. 
hold it in place in the hole and tighten the two screws, which presses the two parts against the hole and holds it securely in place.
Ready to drill with a perfect center guide. :-D